Power system and method for adjusting a release voltage of a bi-directional converter

ABSTRACT

A method for adjusting a release voltage of a power system. The power converter has a power input terminal for receiving a bus voltage, a first resistor coupled between the power input terminal and a sense terminal, a second resistor coupled between the sense terminal and a reference ground, and a bi-directional converter having a first terminal coupled to the power input terminal. The bi-directional converter converts the bus voltage received at the first terminal to a first voltage at a second terminal or converts the first voltage to the release voltage at the first terminal. The method is adjusting the release voltage by changing the ratio of the first resistor to the second resistor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Chinese Patent Application No. 202010815729.X, filed on Aug. 13, 2020, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

This disclosure generally relates to a power system, and more particularly but not exclusively relates to a power system having a bi-directional converter.

BACKGROUND

Today, a bi-directional converter is well designed for some uninterruptable power applications. When there is a power source for the bi-directional converter, the bi-directional converter works in a first mode to transfer energy from the power source to a storage capacitor. When there is no power source, the bi-directional converter works in a second mode to provide a release voltage as a backup power for the power system.

For one bi-directional converter, the release voltage is supposed to be adjustable to meet different requirements. Usually the release voltage is adjusted by some communication pins or a feedback pin of the bi-directional converter, but if the release voltage can be adjusted without a pin, the cost of the bi-directional converter will be decreased.

Therefore, it is desired to design a bi-directional converter that can adjust the release voltage without a pin.

SUMMARY

In accomplishing the above and other objects, there has been provided a power system. The power system comprises a power input terminal configured to receive a bus voltage, a sense terminal configured to provide a sense voltage indicative of the bus voltage and a bi-directional converter having a first terminal coupled to the power input terminal. Wherein when the sense voltage is higher than a reference voltage, the bi-directional converter works in a storage mode, the bi-directional converter converts the bus voltage received at the first terminal to a first voltage at a second terminal. When the sense voltage is lower than the reference voltage, the bi-directional converter works in a release mode, the bi-directional converter converts the first voltage at the second terminal to a release voltage at the first terminal, wherein the bus voltage at the moment when the bi-directional converter transits from the storage mode to the release mode is a transition voltage threshold, and wherein when the transition voltage threshold varies, the release voltage varies.

There has also been provided a power system. The power system comprises a power input terminal configured to receive a bus voltage, a sense terminal configured to provide a sense voltage indicative of the bus voltage, a first resistor coupled between the power input terminal and the sense terminal, a second resistor coupled between the sense terminal and a reference ground, and a bi-directional converter having a first terminal coupled to the power input terminal. Wherein when the sense voltage is higher than a reference voltage, the bi-directional converter converts the bus voltage received at the first terminal to a first voltage at the second terminal. When the sense voltage is lower than the reference voltage, the bi-directional converter converts the first voltage at the second terminal to a release voltage at the first terminal. Wherein when the ratio of the first resistor to the second resistor varies, the release voltage varies.

There has also been provided a method for adjusting a release voltage of a power system. The power system has a power input terminal to receive a bus voltage, and a bi-directional converter having a first terminal coupled to the power input terminal, the bi-directional converter is configured to work in a storage mode to convert the bus voltage to a first voltage or work in a release mode to convert the first voltage to the release voltage, wherein the method comprises adjusting the release voltage by changing a transition voltage threshold, and wherein the transition voltage threshold is the bus voltage at the moment when the bi-directional converter transits from the storage mode to the release mode.

There has also been provided a method for adjusting a release voltage of a power system. The power system has a power input terminal to receive a bus voltage, a first resistor coupled between the power input terminal and a sense terminal, a second resistor coupled between the sense terminal and a reference ground, and a bi-directional converter having a first terminal coupled to the power input terminal, the bi-directional converter is configured to convert the bus voltage received at the first terminal to a first voltage at a second terminal or convert the first voltage to the release voltage at the first terminal, wherein the method comprises adjusting the release voltage by changing the ratio of the first resistor to the second resistor

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of various embodiments of the present invention can best be understood when read in conjunction with the following drawings, in which the features are not necessarily drawn to scale but rather are drawn as to best illustrate the pertinent features.

FIG. 1 illustrates a schematic diagram of a power system 100 in accordance with an embodiment of the present invention.

FIG. 2 illustrates a schematic diagram of the release voltage setting circuit 14 of FIG. 1 in accordance with an embodiment of the present invention.

FIG. 3 illustrates another schematic diagram of the release voltage setting circuit 14 in accordance with an embodiment of the present invention.

FIG. 4 illustrates a sheet showing the corresponding relation between the transition voltage digital signal D_(UV) and the output control signal VO of the release voltage setting circuit 14 of FIG. 2 in accordance with an embodiment of the present invention.

FIG. 5 illustrates a sheet showing the corresponding relation among the transition voltage digital signal D_(UV), the high side control signal VH and the low side control signal VL of the release voltage setting circuit 14 of FIG. 3 in accordance with an embodiment of the present invention.

FIG. 6A-FIG. 6C illustrate the variation of the release voltage V_(SUP) when the transition voltage threshold V_(UV) increases in accordance with an embodiment of the present invention.

FIG. 7A-FIG. 7C illustrate the variation of the release voltage V_(SUP) when the transition voltage threshold V_(UV) increases in accordance with another embodiment of the present invention.

FIG. 8 illustrates a method 800 of adjusting a release voltage V_(SUP) of a power system in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

Various embodiments of the present invention will now be escribed. In the following description, some specific details, such as example circuits and example values for these circuit components, are included to provide a thorough understanding of the embodiments. One skilled in the relevant art will recognize, however, that the present invention can be practiced without one or more specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, processes or operations are not shown or described in detail to avoid obscuring aspects of the present invention.

Throughout the specification and claims, the term “coupled,” as used herein, is defined as directly or indirectly connected in an electrical or non-electrical manner. The terms “a,” “an,” and “the” include plural reference, and the term “in” includes “in” and “on”. The phrase “in one embodiment,” as used herein does not necessarily refer to the same embodiment, although it may. The term “or” is an inclusive “or” operator, and is equivalent to the term “and/or” herein, unless the context clearly dictates otherwise. The term “based on” is not exclusive and allows for being based on additional factors not described, unless the context clearly dictates otherwise. The term “circuit” means at least either a single component or a multiplicity of components, either active and/or passive, that are coupled together to provide a desired function. The term “signal” means at least one current, voltage, charge, temperature, data, or other signal. Where either a field effect transistor (“FET”) or a bipolar junction transistor (“BJT”) may be employed as an embodiment of a transistor, the scope of the words “gate”, “drain”, and “source” includes “base”, “collector”, and “emitter”, respectively, and vice versa. Those skilled in the art should understand that the meanings of the terms identified above do not necessarily limit the terms, but merely provide illustrative examples for the terms.

FIG. 1 illustrates a schematic diagram of a power system 100 in accordance with an embodiment of the present invention. The power system 100 comprises a power input terminal IN to receive a bus voltage V_(BUS), a feedback circuit 11 and a bi-directional converter 12. The feedback circuit 11 receives the bus voltage V_(BUS) and generates a sense voltage V_(SEN) at a sense terminal SEN indicative of the bus voltage V_(BUS). The bi-directional converter 12 has a first terminal 111 coupled to the power input terminal IN and a second terminal 112 coupled to a storage capacitance C_(S). The bi-directional converter 12 can work in a storage mode or a release mode based on the sense voltage V_(SEN). When the sense voltage V_(SEN) is higher than a reference voltage V_(REF), the bi-directional converter 12 works in the storage mode, the bi-directional converter 12 converts the bus voltage V_(BUS) received at the first terminal 111 to a first voltage V1 at the second terminal 112 to charge the storage capacitance C_(S). When the sense voltage V_(SEN) is lower than the reference voltage V_(REF), the bi-directional converter 12 works in the release mode, the bi-directional converter 12 converts the first voltage V1 at the second terminal 112 to a release voltage V_(SUP) at the first terminal 111, wherein the bus voltage V_(BUS) at the moment when the bi-directional converter 12 transits from the storage mode to the release mode is defined as a transition voltage threshold V_(UV). The transition voltage threshold V_(UV) is adjusted by the feedback circuit 11, and the release voltage V_(SUP) can be adjusted by the transition voltage threshold V_(UV). In an embodiment, the first voltage V1 is lower than the bus voltage V_(BUS). In another embodiment, the release voltage V_(SUP) is higher than the first voltage V1. In an embodiment, the bi-directional converter 12 comprises a converter circuit which can be configured as a buck circuit working for the storage mode or a boost circuit working for the release mode. In the exemplary embodiment of FIG. 1 , the power system 100 may further comprise M switching circuits CT1, CT2, . . . , CTM for providing M output voltages V_(S1), V_(S2), . . . , V_(SM) respectively, wherein M is an integer greater than or equal to 1. Each switching circuit has an input terminal coupled to the first terminal 111 of the bi-directional converter 12 to receive the bus voltage V_(BUS) or the release voltage V_(SUP), and an output terminal to output the responding output voltage. In an embodiment, the M output voltages V_(S1), V_(S2), . . . , V_(SM) may have different values to meet specific requirements. In the exemplary embodiment of FIG. 1 , the power system 100 may further comprise M switching capacitors C1, C2, . . . , CM, wherein the i^(th) switching capacitor Ci is coupled to the output terminal of the i^(th) switching circuit CTi for receiving the i^(th) output voltage V_(Si), wherein i is an integer from 1 to M. When the sense voltage V_(SEN) is higher than the reference voltage V_(REF), the bi-directional converter 12 works in the storage mode, the M switching circuits CT1, CT2, . . . , CTM are powered by the bus voltage V_(BUS) received from the power input terminal IN. When the sense voltage V_(SEN) is lower than the reference voltage V_(REF), the bi-directional converter 12 works in the release mode to provide the release voltage V_(SUP), and the M switching circuits CT1, CT2, . . . , CTM are powered by the release voltage V_(SUP). In an embodiment, one or some of the M switching circuits CT1, CT2, . . . , CTM can be fabricated in the same semiconductor substrate making of the bi-directional converter 12.

In the exemplary embodiment of FIG. 1 , the feedback circuit 11 comprises a first resistor R1 and a second resistor R2, wherein the first resistor R1 has a first terminal coupled to the power input terminal IN to receive the bus voltage V_(BUS), and a second terminal coupled to the sense terminal SEN. The second resistor R2 has a first terminal coupled to the sense terminal SEN, and a second terminal coupled to a reference ground GND. The transition voltage threshold V_(UV) can be adjusted by changing the ratio of the first resistor R1 to the second resistor R2.

The exemplary power system 100 may further comprise a mode control circuit CMP. The mode control circuit CMP receives the sense voltage V_(SEN) from the sense terminal SEN and generates a mode signal PF by comparing the sense voltage V_(SEN) with the reference voltage V_(REF). When the sense voltage V_(SEN) is higher than the reference voltage V_(REF), the mode signal PF is in a first state to control the bi-directional converter 12 to work in the storage mode. When the sense voltage V_(SEN) is lower than the reference voltage V_(REF), the mode signal PF is in a second state to control the bi-directional converter 12 to work in the release mode.

Still referring to FIG. 1 , the power system 100 may further comprise a protection circuit 13. When the sense voltage V_(SEN) is higher than the reference voltage V_(REF), the protection circuit 13 can be seen as a conductive line, the bus voltage V_(BUS) transits to the power input terminal IN through the protection circuit 13. When the sense voltage V_(SEN) is lower than the reference voltage V_(REF), the protection circuit 13 may block a reverse current coming from the power input terminal IN. Persons with ordinary skills in this art should know that the protection circuit 13 may be integrated with the bi-directional converter 12 in the same semiconductor substrate. The protection circuit 13 can also be realized by discrete devices, such as a discrete diode D1 illustrated in FIG. 1 . In an embodiment, the protection circuit 13 comprises a MOSFET.

Continuing with FIG. 1 , the power system 100 further comprises a release voltage setting circuit 14. The release voltage setting circuit 14 receives the bus voltage V_(BUS) and the mode signal PF, and records the bus voltage V_(BUS) at the moment when the mode signal PF transits from the first state to the second state, i.e., the release voltage setting circuit 14 records the transition voltage threshold V_(UV). The release voltage setting circuit 14 further generates an output control signal VO based on the transition voltage threshold V_(UV) to control the release voltage V_(SUP). In an embodiment, the release voltage setting circuit 14 is configured to generate a high side control signal VH and a low side control signal VL based on the transition voltage threshold V_(UV) to control the release voltage V_(SUP). In an embodiment, the release voltage V_(SUP) equals the average value of the high side control signal VH and the low side control signal VL. In an embodiment, the high side control signal VH is fixed. In an embodiment, when the transition voltage threshold V_(UV) increases, the release voltage V_(SUP) increases. In an embodiment, when the transition voltage threshold V_(UV) increases, the release voltage V_(SUP) decreases.

FIG. 2 illustrates a schematic diagram of the release voltage setting circuit 14 of FIG. 1 in accordance with an embodiment of the present invention. In the exemplary embodiment of FIG. 2 , the release voltage setting circuit 14 comprises a threshold recording circuit 141 a, a coding circuit 142 a and a decoding circuit 143 a. The threshold recording circuit 141 a is configured to generate the transition voltage threshold V_(UV) based on the bus voltage V_(BUS) and the mode signal PF. The coding circuit 142 a receives the transition voltage threshold V_(UV) and generates a transition voltage digital signal D_(UV) based on the transition voltage threshold V_(UV). In an embodiment, the transition voltage digital signal D_(UV) is generated by coding the transition voltage threshold V_(UV) according to a predetermined coding rule. The decoding circuit 143 a receives the transition voltage digital signal D_(UV) and generates the output control signal VO based on the transition voltage digital signal D_(UV) to control the release voltage V_(SUP). In an embodiment, the output control signal VO is generated by decoding the transition voltage digital signal D_(UV) according to a predetermined decoding rule. The working principle of the coding circuit 142 a and the decoding circuit 143 a will be described together for better understanding. For the coding circuit 142 a, N voltage regions RG1, RG2, . . . , RGN are programmed in it and the transition voltage threshold V_(UV) is in one of the N voltage regions RG1, RG2, . . . , RGN. The transition voltage digital signal D_(UV) may have N coding values D1, D2, . . . , DN in response to the N voltage regions RG1, RG2, . . . , RGN respectively, and the output control signal VO has N decoding values VO1, VO2, . . . , VON in response to the N coding values D1, D2, . . . , DN respectively, wherein N is an integer greater than 1 and is determined by the bit of the coding circuit 142 a. When the transition voltage threshold V_(UV) is in one voltage region, the transition voltage digital signal D_(UV) may have a corresponding coding value and the output control signal VO may have a corresponding decoding value accordingly. For example, if the transition voltage threshold V_(UV) is in the i^(th) voltage region RGi, the transition voltage digital signal D_(UV) may have the i^(th) coding value Di, and the output control signal VO may have the i^(th) decoding value VOi, wherein i is an integer from 1 to N.

FIG. 3 illustrates another schematic diagram of the release voltage setting circuit 14 in accordance with an embodiment of the present invention. In the exemplary embodiment of FIG. 3 , the release voltage setting circuit 14 comprises a threshold recording circuit 141 b, a coding circuit 142 b and a decoding circuit 143 b. The threshold recording circuit 141 b receives the bus voltage V_(BUS) and the mode signal PF, and is configured to record the transition voltage threshold V_(UV). The coding circuit 142 b receives the transition voltage threshold V_(UV) and generates the transition voltage digital signal D_(UV) based on the transition voltage threshold V_(UV). In an embodiment, the transition voltage digital signal D_(UV) is generated by coding the transition voltage threshold V_(UV) according to a predetermined code rule. The decoding circuit 143 b receives the transition voltage digital signal D_(UV) from the coding circuit 142 b and generates the high side control signal VH and the low side control signal VL based on the transition voltage digital signal D_(UV) to control the release voltage V_(SUP). In an embodiment, the high side control signal VH and the low side control signal VL are generated by decoding the transition voltage digital signal D_(UV) according to a predetermined decoding rule. The working principle of the coding circuit 142 b and the decoding circuit 143 b will be described together for better understanding. For the coding circuit 142 b, N voltage regions RG1, RG2, . . . , RGN are programmed in it and the transition voltage threshold V_(UV) is in one of the N voltage regions RG1, RG2, . . . , RGN. The transition voltage digital signal D_(UV) may have N coding values D1, D2, . . . , DN in response to the N voltage regions RG1, RG2, . . . , RGN respectively, the high side control signal VH has N high side values VH1, VH2, . . . , VHN in response to the N coding values D1, D2, . . . , DN respectively, and the low side control signal VL has N low side values VL1, VL2, . . . , VLN in response to the N coding values D1, D2, . . . , DN respectively, wherein N is an integer greater than 1 and is determined by the bit of the coding circuit 142 b. In an embodiment, the release voltage V_(SUP) equals the average value of the high side control signal VH and the low-side control signal VL. In another embodiment, the high side control signal VH is fixed, i.e., VH1=VH2= . . . VHN. In the exemplary embodiment of FIG. 3 , the decoding circuit 143 b may further generate an indication signal VPG based on the transition voltage digital signal D_(UV). The indication signal VPG has N indication values VPG1, VPG2, . . . , VPGN in response to the N coding values D1, D2, . . . , DN respectively. In other embodiments, The decoding circuit 143 b further generates a current peak signal IPK to control the current limit of the bi-directional converter 12, the current peak signal IPK has N current values IPK1, IPK2, . . . , IPKN in response to the N coding values D1, D2, . . . , DN respectively. In an embodiment, the decoding circuit 143 b may further generate a plurality of analogy control signals configured to control some electric parameters of the bi-directional converter 12, wherein one or some of the plurality of analogy control signals may be configured to control one electric parameter of the bi-directional converter 12.

FIG. 4 illustrates a sheet showing the corresponding relation between the transition voltage digital signal D_(UV) and the output control signal VO of the release voltage setting circuit 14 of FIG. 2 in accordance with an embodiment of the present invention. Assuming the coding circuit 142 a and the decoding circuit 143 a are 3 bits, so voltage regions RG1, RG2, . . . , RG8 are programmed in the coding circuit 142 a. If the transition voltage threshold V_(UV) is in the first voltage region RG1, the transition voltage digital signal D_(UV) has a first coding value D1, and the output control signal VO has a first decoding value VO1. The transition voltage threshold V_(UV) is adjustable, for example, when the transition voltage threshold V_(UV) is changed from the first voltage region RG1 to the second voltage region RG2, the transition voltage digital signal D_(UV) is changed from the first coding value D1 to the second coding value D2, and the output control signal VO is changed from the first decoding value VO1 to the second decoding value VO2 accordingly.

FIG. 5 illustrates a sheet showing the corresponding relation among the transition voltage digital signal D_(UV), the high side control signal VH and the low side control signal VL of the release voltage setting circuit 14 of FIG. 3 in accordance with an embodiment of the present invention. Assuming the coding circuit 142 b and the decoding circuit 143 b are 3 bits, so voltage regions RG1, RG2, . . . , RG8 are programmed in the coding circuit 142 b. If the transition voltage threshold V_(UV) is in the first voltage region RG1, the transition voltage digital signal D_(UV) has a first coding value D1, the high side control signal VH has a first high side value VH1, and the low side control signal VL has a first low side value VL1. The transition voltage threshold V_(UV) is adjustable, for example, when the transition voltage threshold V_(UV) is changed from the first voltage region RG1 to the second voltage region RG2, the transition voltage digital signal D_(UV) is changed from the first coding value D1 to the second coding value D2, the high side control signal VH is changed from the first high side value VH1 to the second high side value VH2, and the low side control signal VL is changed from the first low side value VL1 to the second low side value VL2 accordingly.

Persons with ordinary skills in this art should know that the adjusting accuracy of the release voltage V_(SUP) can be improved if the coding circuit and decoding circuit have more bits.

FIG. 6A-FIG. 6C illustrate the variation of the release voltage V_(SUP) when the transition voltage threshold V_(UV) increases in accordance with an embodiment of the present invention. The waveforms of the sense signal V_(SEN), the reference voltage V_(REF), the mode signal PF, the bus voltage V_(BUS) and the release voltage V_(SUP) are all shown with reference for better illustration. Assuming the reference voltage V_(REF) is 1V, when the bus voltage V_(BUS) decreases, the sense voltage V_(SEN) decreases. The sense voltage V_(SEN) drops to the reference voltage V_(REF) at the moment t1, so the mode signal PF transits from the first state to the second state and the bi-directional converter 12 transits from the storage mode to the release mode for providing the release voltage V_(SUP) at the moment t1. In FIG. 6A, the transition voltage threshold V_(UV) is in the first voltage region RG1, thus the high side control signal VH equals the first high side value VH1, and the low side control signal VL equals the first low side value VL1. The release voltage V_(SUP) equals the average value of the high side control signal VH and the low side control signal, i.e., V_(SUP)=(VH+VL)/2=(VH1+VL1)/2. In the exemplary embodiment of FIG. 6A, the bi-directional converter 12 working in the release mode is a boost circuit having a first power switch and a second power switch, and the release voltage V_(SUP) is regulated by controlling the on and off switching of the first power switch and the second power switch.

In FIG. 6B, the transition voltage threshold V_(UV) is increased to the i^(th) voltage region RGi by adjusting the ratio of the first resistor R1 to the second resistor R2. For example, the ratio of the first resistor R1 to the second resistor R2 can be adjusted by changing the resistance of the first resistor R1 or the resistance of the second resistor R2. At the moment t2, the sense voltage V_(SEN) drops to the reference voltage V_(REF), so the mode signal PF transits from the first state to the second state and the bi-directional converter 12 transits from the storage mode to the release mode for providing the release voltage V_(SUP). The bus voltage V_(BUS) at the moment t2 is the transition voltage threshold V_(UV), and the transition voltage threshold V_(UV) in FIG. 6B is increased to the i^(th) voltage region RGi. In FIG. 6B, the transition voltage threshold V_(UV) is in the i^(th) voltage region RGi, the high side control signal VH equals the i^(th) high side value VHi, the low side control signal VL equals the i^(th) low side value VLi, and the release voltage V_(SUP) equals the average value of the high side control signal VH and the low side control signal VL, i.e., V_(SUP)=(VH+VL)/2=(VHi+VLi)/2.

In FIG. 6C, the transition voltage threshold V_(UV) is increased to the N^(th) voltage region RGN by adjusting the ratio of the first resistor R1 to the second resistor R2. For example, the ratio of the first resistor R1 to the second resistor R2 can be adjusted by changing the resistance of the first resistor R1 or the resistance of the second resistor R2. At the moment t3, the sense voltage V_(SEN) drops to the reference voltage V_(REF), so the mode signal PF transits from the first state to the second state and the bi-directional converter 12 transits from the storage mode to the release mode for providing the release voltage V_(SUP). The bus voltage V_(BUS) at the moment t3 is the transition voltage threshold V_(UV), and the transition voltage threshold V_(UV) in FIG. 6C is increased to the N^(th) voltage region RGN. In FIG. 6C, the transition voltage threshold V_(UV) is in the N^(th) voltage region RGN, the high side control signal VH equals the N^(th) high side value VHN, and the low side control signal VL equals the N^(th) low side value VLN. The release voltage V_(SUP) equals the average value of the high side control signal VH and the low side control signal VL, i.e., V_(SUP)=(VH+VL)/2=(VHN+VLN)/2.

It can be seen from FIG. 6A-FIG. 6C that the release voltage V_(SUP) increases when the transition voltage threshold V_(UV) varies. Specifically, when the transition voltage threshold V_(UV) increases, the release voltage V_(SUP) increases. In an embodiment, when the ratio of the first resistor R1 to the second resistor R2 increases, the transition voltage threshold V_(UV) increases, and the release voltage V_(SUP) increases accordingly. In another embodiment, when the ratio of the first resistor R1 to the second resistor R2 increases, the transition voltage threshold V_(UV) decreases, and the release voltage V_(SUP) decreases accordingly.

FIG. 7A-FIG. 7C illustrate the variation of the release voltage V_(SUP) when the transition voltage threshold V_(UV) is changed in accordance with another embodiment of the present invention. The waveforms of the sense voltage V_(SEN), the reference voltage V_(REF), the mode signal PF, the bus voltage V_(BUS) and the release voltage V_(SUP) are all shown for better illustration. The high side control signal VH of FIG. 7A-FIG. 7C is fixed, which is different from FIG. 6A-FIG. 6C. Assuming the reference voltage V_(REF) is 1V, when the bus voltage V_(BUS) decreases, the sense voltage V_(SEN) decreases. The sense voltage V_(SEN) drops to the reference voltage V_(REF) at the moment t4, so the mode signal PF transits from the first state to the second state and the bi-directional converter 12 transits from the storage mode to the release mode for providing the release voltage V_(SUP) at the moment t4, the value of the bus voltage V_(BUS) at the moment t4 is the transition voltage threshold V_(UV). In FIG. 7A, the transition voltage threshold V_(UV) is in the first voltage region RG1, thus the high side control signal VH equals the first high side value VH1, and the low side control signal VL equals the first low side value VL1, the release voltage V_(SUP) equals the average of the high side control signal VH and the low side control signal VL, i.e., V_(SUP)=(VH+VL)/2=(VH 1+VL1)/2.

In FIG. 7B, the transition voltage threshold V_(UV) is increased to the i^(th) voltage region RGi by adjusting the ratio of the first resistor R1 to the second resistor R2. For example, the ratio of the first resistor R1 to the second resistor R2 can be adjusted by changing the resistance of the first resistor R1 or the resistance of the second resistor R2. At the moment t5, the sense voltage V_(SEN) drops to the reference voltage V_(REF), so the mode signal PF transits from the first state to the second state and the bi-directional converter 12 transits from the storage mode to the release mode for providing the release voltage V_(SUP). The bus voltage V_(BUS) at the moment t5 is the transition voltage threshold V_(UV), so the transition voltage threshold V_(UV) in FIG. 7B is increased to the i^(th) voltage region RGi. In FIG. 7B, the transition voltage threshold V_(UV) is in the i^(th) voltage region RGi, the high side control signal VH equals the i^(th) high side value VHi, the low side control signal VL equals the i^(th) low side value VLi, and the release voltage V_(SUP) equals the average value of the high side control signal VH and the low side control signal VL, i.e., V_(SUP)=(VH+VL)/2=(VHi+VLi)/2.

In FIG. 7C, the transition voltage threshold V_(UV) is increased to the N^(th) voltage region RGN by adjusting the ratio of the first resistor R1 to the second resistor R2. At the moment t6, the sense voltage V_(SEN) drops to the reference voltage V_(REF), so the mode signal PF transits from the first state to the second state and the bi-directional converter 12 transits from the storage mode to the release mode for providing the release voltage V_(SUP). The bus voltage V_(BUS) at the moment t6 is the transition voltage threshold V_(UV), so the transition voltage threshold V_(UV) in FIG. 7C is increased to the N^(th) voltage region RGN, the high side control signal VH equals the N^(th) high side value VHN, and the low side control signal VL equals the N^(th) low side value VLN. The release voltage V_(SUP) equals the average value of the high side control signal VH and the low side control signal VL, i.e., V_(SUP)=(VH+VL)/2=(VHN+VLN)/2.

In the exemplary embodiment of FIG. 7A-FIG. 7C, when the transition voltage threshold V_(UV) increases, the release voltage V_(SUP) increases. In other embodiments, when the transition voltage threshold V_(UV) increases, the release voltage V_(SUP) may decrease.

FIG. 8 illustrates a method 800 of adjusting a release voltage V_(SUP) of a power system in accordance with an embodiment of the present invention. The method 800 will be illustrated with reference to the power system 100 for better understanding. The power system 100 has the power input terminal IN to receive the bus voltage V_(BUS), the first resistor R1 coupled between the power input terminal IN and the sense terminal SEN, the second resistor R2 coupled between the sense terminal SEN and the reference ground GND, and the bi-directional converter 12. The bi-directional converter 12 has the first terminal 111 coupled to the power input terminal IN, and the second terminal 112. The method 800 comprises step 801 and step 802. In step 801, generating the sense voltage V_(SEN) indicative of the bus voltage V_(BUS) at the sense terminal SEN. When the sense voltage V_(SEN) is higher than the reference voltage V_(REF), the bi-directional converter 12 works in the storage mode and converts the received bus voltage V_(BUS) to the first voltage V1 to charge the storage capacitor C_(S). When the sense voltage V_(SEN) is lower than the reference voltage V_(REF), the bi-directional converter 12 works in the release mode, the bi-directional converter 12 converts the first voltage V1 to the release voltage V_(SUP). The bus voltage V_(BUS) at the moment when the bi-directional converter 12 transits from the storage mode to the release mode is the transition voltage threshold V_(UV). In step 802, adjusting the release voltage V_(SUP) by changing the ratio of the first resistor R1 to the second resistor R2. In an embodiment, when the ratio of the first resistor R1 to the second resistor R2 increases, the release voltage V_(SUP) increases. In another embodiment, when the ratio of the first resistor R1 to the second resistor R2 increases, the release voltage V_(SUP) may decrease.

In an embodiment, the method 800 of adjusting the release voltage V_(SUP) of a power system may comprise adjusting the release voltage V_(SUP) by changing the transition voltage threshold V_(UV). In an embodiment, the step of adjusting the release voltage V_(SUP) by changing the transition voltage threshold V_(UV) may comprise recording the transition voltage threshold V_(UV), generating the transition voltage digital signal D_(UV) based on the transition voltage threshold V_(UV), generating the output control signal VO based on the transition voltage digital signal D_(UV), and regulating the release voltage V_(SUP) based on the output control signal VO. In other embodiment, the step of adjusting the release voltage V_(SUP) by changing the transition voltage threshold V_(UV) may comprise recording the transition voltage threshold V_(UV), generating the transition voltage digital signal D_(UV) based on the transition voltage threshold V_(UV), generating the high side control signal VH and the low side control signal VL based on the transition voltage digital signal D_(UV), and regulating the release voltage V_(SUP) based on the high side control signal VH and the low side control signal VL. In an embodiment, the release voltage V_(SUP) equals the average value of the high side control signal VH and the low side control signal VL.

In an embodiment, when the bi-directional converter 12 works in the storage mode, the first voltage V1 is lower than the bus voltage V_(BUS), and when the bi-directional converter 12 works in the release mode, the release voltage V_(SUP) is higher than the first voltage V1.

For the power system in accordance with various embodiments of the present invention, when the bus voltage V_(BUS) is higher than the transition voltage threshold V_(UV), the bus voltage V_(BUS) is configured to power the bi-directional converter and the switching circuits in the power system, and when the bus voltage V_(BUS) is lower than the transition voltage threshold V_(UV), the bi-directional converter provides the release voltage V_(SUP) to supply the switching circuits in the power system. For the power system of the present invention, the release voltage V_(SUP) is adjusted by changing the ratio of the first resistor R1 to the second resistor R2, no need for an additional feedback pin or other communication pins, such as I2C, PBUS, thus at least one feedback pin is omitted, and the cost of the power system is decreased.

The advantages of the various embodiments of the present invention are not confined to those described above. These and other advantages of the various embodiments of the present invention will become more apparent upon reading the whole detailed descriptions and studying the various figures of the drawings.

From the foregoing, it will be appreciated that specific embodiments of the present invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the technology. Many of the elements of one embodiment may be combined with other embodiments in addition to or in lieu of the elements of the other embodiments. Accordingly, the present invention is not limited except as by the appended claims. 

What is claimed is:
 1. A power system, comprising: a power input terminal, configured to receive a bus voltage; a sense terminal, configured to provide a sense voltage indicative of the bus voltage; and a bi-directional converter, having a first terminal coupled to the power input terminal, and a second terminal; wherein when the sense voltage increases to reach or to be higher than a reference voltage, the bi-directional converter is adapted to be configured to operate in a storage mode in which the bi-directional converter converts the bus voltage received at the first terminal to a first voltage at the second terminal; and wherein when the sense voltage decreases to reach or to be lower than the reference voltage, the bi-directional converter is adapted to be configured to operate in a release mode in which the bi-directional converter converts the first voltage at the second terminal to a release voltage at the first terminal, and wherein the bus voltage at a moment when the bi-directional converter transits from the storage mode to the release mode is a transition voltage threshold, and wherein when the transition voltage threshold varies, the release voltage varies.
 2. The power system of claim 1, wherein when the transition voltage threshold increases, the release voltage increases.
 3. The power system of claim 1, wherein when the transition voltage threshold decreases, the release voltage decreases.
 4. The power system of claim 1 further comprises: a first resistor, coupled between the power input terminal and the sense terminal; and a second resistor, coupled between the sense terminal and a reference ground; wherein when a ratio of the first resistor to the second resistor varies, the transition voltage threshold varies.
 5. The power system of claim 1 further comprises a mode control circuit, wherein the mode control circuit is configured to generate a mode signal by comparing the sense voltage with the reference voltage, and wherein when the sense voltage increases to reach or to be higher than the reference voltage, the mode signal is in a first state and is adapted to control the bi-directional converter to work in the storage mode, and wherein when the sense voltage decreases to reach or to be lower than the reference voltage, the mode signal is in a second state and is adapted to control the bi-directional converter to work in the release mode.
 6. The power system of claim 1 further comprises a release voltage setting circuit, wherein the release voltage setting circuit comprises: a threshold recording circuit, configured to record the transition voltage threshold; a coding circuit, configured to generate a transition voltage digital signal based on the transition voltage threshold; and a decoding circuit, configured to generate an output control signal to control the release voltage based on the transition voltage digital signal.
 7. The power system of claim 1 further comprises a release voltage setting circuit, wherein the release voltage setting circuit comprises: a threshold recording circuit, configured to record the transition voltage threshold; a coding circuit, configured to generate a transition voltage digital signal based on the transition voltage threshold; and a decoding circuit, configured to generate a high side control signal and a low side control signal to control the release voltage based on the transition voltage digital signal.
 8. The power system of claim 7, wherein the release voltage equals an average value of the high side control signal and the low side control signal.
 9. The power system of claim 1, wherein the first voltage is lower than the bus voltage, and the release voltage is higher than the first voltage.
 10. A power system, comprising: a power input terminal, configured to receive a bus voltage; a sense terminal, configured to provide a sense voltage indicative of the bus voltage; a first resistor, coupled between the power input terminal and the sense terminal; a second resistor, coupled between the sense terminal and a reference ground; and a bi-directional converter, having a first terminal coupled to the power input terminal, and a second terminal; wherein when the sense voltage increases to reach or to be higher than a reference voltage, the bi-directional converter is adapted to be configured to convert the bus voltage received at the first terminal to a first voltage at the second terminal; and wherein when the sense voltage decreases to reach or to be lower than the reference voltage, the bi-directional converter is adapted to be configured to convert the first voltage at the second terminal to a release voltage at the first terminal, and wherein when a ratio of the first resistor to the second resistor varies, the release voltage varies.
 11. The power system of claim 10, wherein when the ratio of the first resistor to the second resistor increases, the release voltage increases.
 12. The power system of claim 10, wherein when the ratio of the first resistor to the second resistor decreases, the release voltage decreases.
 13. A method for adjusting a release voltage of a power system, the power system having a power input terminal to receive a bus voltage, and a bi-directional converter having a first terminal coupled to the power input terminal, the bi-directional converter is configured to work in a storage mode to convert the bus voltage to a first voltage or work in a release mode to convert the first voltage to the release voltage, wherein the method comprises adjusting the release voltage by changing a transition voltage threshold, and wherein the transition voltage threshold is the bus voltage at a moment when the bi-directional converter transits from the storage mode to the release mode.
 14. The method of claim 13, wherein the step of adjusting the release voltage by changing the transition voltage threshold comprises: generating a transition voltage digital signal based on the transition voltage threshold; generating an output control signal based on the transition voltage digital signal; and regulating the release voltage based on the output control signal.
 15. The method of claim 13, wherein the step of adjusting the release voltage by changing the transition voltage threshold comprises: generating a transition voltage digital signal based on the transition voltage threshold; generating a high side control signal and a low side control signal based on the transition voltage digital signal; and regulating the release voltage based on the high side control signal and the low side control signal.
 16. The method of claim 15, wherein the release voltage equals an average value of the high side control signal and the low side control signal.
 17. The method of claim 13, wherein the first voltage is lower than the bus voltage, and the release voltage is higher than the first voltage.
 18. A method for adjusting a release voltage of a power system, the power system having a power input terminal to receive a bus voltage, a first resistor coupled between the power input terminal and a sense terminal, a second resistor coupled between the sense terminal and a reference ground, and a bi-directional converter having a first terminal coupled to the power input terminal, the bi-directional converter is configured to convert the bus voltage received at the first terminal to a first voltage at a second terminal or convert the first voltage to the release voltage at the first terminal, wherein the method comprises adjusting the release voltage by changing a ratio of the first resistor to the second resistor.
 19. The method of claim 18, wherein when the ratio of the first resistor to the second resistor increases, the release voltage increases.
 20. The method of claim 18, wherein when the ratio of the first resistor to the second resistor decreases, the release voltage decreases. 